1. Field of the Invention
This invention relates to an improved cooking and heating apparatus for food. More particularly, this invention relates to an improved food cooking and heating apparatus which maintains heated food temperature without rapid deterioration of food quality by regulation of the amount of air flow through the apparatus.
2. Description of the Prior Art
Food cooking and heating cabinets are well-known devices used to cook food slowly and used to maintain heated food at serving temperature. Cooking and holding cabinets have become valuable tools in the food industry, particularly in fast food and institutional applications. They allow food to be cooked in advance and then held at the desired serving temperature. The cabinet must be large enough to hold many servings, yet maintain a uniform temperature throughout. The food texture, moisture, color, and flavor must be maintained during the time period the food is held in the cabinet. The most important quality to be maintained is food moisture. This concern is specifically identified in Roderick (U.S. Pat. No. 4,039,776), column 1, lines 18-42.
A patentability search was conducted on the present invention and the following U.S. patents were uncovered in the search:
______________________________________ U.S. Pat. No. Patentee Issue Date ______________________________________ 4,302,631 Chesnut et al. November 24, 1981 3,868,941 Roderick March 4, 1975 3,955,007 Roderick May 4, 1976 3,999,475 Roderick December 28, 1976 4,036,776 Roderick August 2, 1977 4,062,983 Roderick December 13, 1977 3,634,651 Siegel et al. January 11, 1972 3,737,622 Hallgreen June 2, 1971 238,471 Woods March 1, 1881 3,885,126 Sugiyama et al. May 20, 1975 4,030,476 Hock June 21, 1977 4,208,572 Melgaard June 17, 1980 4,250,955 Plattner et al. February 17, 1981 ______________________________________
Early cooking and heating cabinets utilized radiant heating of the oven. The Roderick patents (U.S. Pat. Nos. 3,868,941 and 3,955,007) are examples of the prior art. A heated outer jacket transfers heat through the oven walls to heat the food therein. The next advance in the art is seen in Roderick (U.S. Pat. No. 4,039,776) where the heated jacket is closed and the air therein recirculated. These approaches suffer two major drawbacks. First, it has been impossible to achieve uniform heat in the larger cabinets presently in use. Second, an unduly long period of time is required to recover the desired temperature after the oven door is opened.
For this reason, it has been found advantageous to circulate heated air through the oven and around the food. In practice, the Roderick U.S. Pat. No. 4,039,776 ovens were modified to provide openings in the oven walls to allow a small portion of heated air to circulate through the oven. Hock (U.S. Pat. No. 4,030,476) shows this approach taken a step further. All of the heated air is circulated through the oven and returned to the heating chamber with the use of a blower. A heating element, used to heat the air in a heating chamber, is controlled by a thermostat and a heat sensitive switch. When the air reaches a desired temperature, the heating element is switched off. Uniform heat and quick temperature recovery may be achieved; food quality, however, is decreased due to drying caused by the heated air passing over and around the food.
One approach is shown in Roderick (U.S. Pat. No. 4,062,983). To avoid the drying effect, heated air is circulated in a food chamber in a circular pattern around the food which is centered at the "eye of the tornado", where air circulation is minimized.
Hock and others have attempted to address the problem of deteriorating food quality by adding moisture back into the air. Hock's water pan is positioned so that the heated air flows over the surface of the water. There are two problems that arise. It is believed that decreasing the drying effect and retaining the natural moisture of food is superior to adding moisture to the atmosphere. Additionally, the water pan requires constant refilling, which is time consuming and is often overlooked by restaurant and institutional attendants.
A further problem can be seen in FIG. 7 of Hock. All of the moist, sometimes grease-laden, air flows past the motor and wiring, leading to breakdowns and required cleaning and repair.
Returning to a consideration of Roderick (U.S. Pat. No. 4,039,776), the heating elements and blowers are activated when the heated air drops below a selected lower temperature. When the heated air reaches the selected temperature, and heating element is deactivated and the blowers continue until the temperature begins to drop.
The present invention is an improvement over the hot food holding cabinets such as shown in Hock. A variable speed blower is combined with circuitry responsive to the temperature in the oven.
Therefore, it is a principal object and purpose of the present invention to maximize food quality in a food cooking and heating apparatus by controlling the amount of air passing over and around the food.
It is a further object and purpose of the present invention to provide a food cooking and heating apparatus with an air heating chamber having an improved design, thereby reducing breakdowns and required repairs.